Worked on improving SPI reliability in the Zephyr STM32 SPI driver by addressing data loss issues in Slave Half-Duplex TX mode. The solution involved keeping the SPI peripheral enabled until the master device finished clocking out all data, aligning the behavior with SPI_HOLD_ON_CS to ensure data integrity. This approach reduced the risk of dropped bytes and improved interoperability between master and slave devices. The fix was validated end-to-end on NUCLEO-F439ZI hardware using SPI1 and SPI3 in half-duplex mode. Contributed to the zephyrproject-rtos/zephyr repository using C programming, driver development, and embedded systems expertise to enhance communication reliability.